The present invention relates to a body which is formed at least in regions in a hollow-cylindrical manner, is designated hereinafter as a hollow body and has an integrated oil separating device. Preferably, the hollow body is formed by a camshaft.
PCT publication WO 2006/119737 A1 discloses a hollow shaft having an integrated oil separating device, wherein in addition to a pre-separator, which is disposed on the outer periphery of the shaft, there is provided a swirl generator, which is integrated into the cavity of the shaft, as a final separator.
Furthermore, a camshaft having integrated oil separation is already disclosed in a VDI-report (VDI-Reports no. 2042, 2008, page 152, Chapter 4 and FIG. 6), wherein a helical swirl generator is disposed in the cavity of the camshaft.
Exemplary embodiments of the present invention provide a generic hollow body having an integrated oil separating device which, with production-technology expenditure being kept as low as possible, ensures optimised oil separation from so-called blow-by-gases. Hereinafter, the blow-by-gas will also be referred to as oil mist or oil-charged gas with no change in meaning.
In accordance with the invention, disposed downstream—as seen in the flow direction—of the swill generator which is integrated into a hollow body and forms in this case a first (inner) oil separating stage, is an oil separating ring (acting as a second (inner) oil separating stage) (disposed coaxially in the cavity of the hollow body).
The swirl generator is advantageously formed as a body extending in the axial direction of the hollow body and comprising or forming at least one screw channel on the periphery which means that at least one flow channel is formed by the screw channel between the body of the swirl generator and the inner wall of the hollow body in order to guide the oil-charged gas fed into the camshaft and to separate oil particles on the inner wall-side. The blow-by-gas, which is to have the oil removed therefrom, flows through at least one bore disposed tangentially to the inner wall of the hollow body. For the introduction of the blow-by-gas, several bores are advantageously provided, wherein preferably each of the bores is disposed in particular tangentially to the inner wall of hollow body and the bores are disposed so as to be axially offset with respect to each other. In terms of the invention, a bore extending tangentially to the inner wall of the hollow body is to be understood to mean one positioned in a manner different from a radial arrangement of a bore such that the bore merges without any transitions (continuously) into the progression of the inner wall of the hollow body, which progression is circular as seen in cross-section, i.e., that a bore casing line extending in parallel with the bore longitudinal axis is disposed tangentially to the inner wall of the hollow body, which inner wall is circular as seen in cross-section.
In a particularly preferred embodiment of the invention, the body of the swirl generator comprises, at least in regions, a second screw channel. Two flow paths extending in parallel are hereby formed, at least in regions. The design of the hollow body having two screw channels is advantageously provided in the starting region of the swirl generator and the supply openings are arranged such that the oil-charged air (blow-by-gas) flowing in—substantially without any fluidic resistance or with minimized fluidic resistance—is fed to the interior of the hollow body. Since the blow-by-gas is aspirated into the cavity of the hollow body substantially by a negative pressure produced in the interior of the hollow body, the attempt is made to substantially maintain this negative pressure by minimizing fluidic resistance. The required negative pressure can be produced, for example, by a pump coupled to the cavity of the camshaft. The second screw channel is advantageously formed such that it extends approximately over half of a complete volution of a total of 360°.
The or each screw channel can be formed such that the pitch of the respective screw channel varies. The pitches of the two screw channels are preferably the same size, wherein the pitch is predetermined as a whole by the first (longer) screw channel or is dependent upon the requirements placed thereon. The pitch advantageously varies such that the distances of the screw walls of a screw channel and thus the cross-section of the flow paths or flow channels formed by the screw walls get smaller. The blow-by-gas is hereby accelerated further during its flow path and the negative pressure existing in the cavity of the hollow body is substantially maintained.
In order to discharge the separated oil and/or the blow-by-gas which has oil cleaned therefrom, one or more discharge openings can be provided in the hollow body on the casing-side, wherein the gas which has oil cleaned therefrom and flows in the axial direction through the hollow body is deflected outwards towards the radial discharge opening(s) by a flow deflection element, which is disposed in the cavity of the hollow body downstream of the discharge openings. The separated oil that flows along the inner wall of the hollow body in the flow direction is diverted from the hollow body by one or more casing-side oil discharge openings disposed upstream of the casing-side discharge openings for the gas as seen in the flow direction.
In a particularly preferred embodiment of the hollow body, it comprises bearing sections at a plurality of locations, via which it co-operates with a corresponding bearing device in the assembled state. These bearing sections are advantageously formed as hardened, smooth surfaces which co-operate with a corresponding bearing body for rotatable mounting of the hollow body. The bearing can be formed as a slide bearing or as any roller bearing. The or each radial discharge opening for draining off the separated oil and/or for draining off the purified blow-by-gas are advantageously disposed in the region of the bearing section. For the continued guidance of the drained-off oil and/or purified blow-by-gas, the bearing device co-operating with the bearing point likewise comprises corresponding discharge openings or discharge channels. The discharge openings and the corresponding discharge channels can be disposed substantially in the same direction and disposed so as to extend in parallel with each other. In another embodiment, it is feasible to dispose the discharge openings for oil or gas so as to be axially offset in each case and opposite each other in the hollow body and in the bearing device.
In another preferred embodiment of the invention, a bypass channel is integrated into the swirl generator. The bypass channel is formed by an axial (through-going) bore, open on both sides, through the hollow body. The bypass bore can be released by an integrated bypass valve dependent upon the pressure. For the fluidic deflection of blow-by-gas, the hollow body comprises at least one further casing-side supply opening for the introduction of oil-charged gas into the cavity of the hollow body. This further supply opening is disposed upstream of the swirl generator on the side of the swirl generator remote from the at least one discharge opening.